A free ink type writing instrument having a collector structure in which a liquid ink is stored directly in a barrel, a writing instrument having a structure in which an ink is stored in an ink reservoir of a cartridge type and a ballpoint pen of a type in which an ink for a ballpoint pen is filled in a transparent refill have so far been known as a writing instrument in which a remaining amount of an ink and a sign of exhausting an ink can be detected.
On the other hand, in a writing instrument in which a pen tip in a writing part is fed with an ink for a writing instrument such as a water-based ink and an oil-based ink impregnated into an ink occlusion body in a barrel, a so-called writing instrument of a sliver type, it is the existing situation that writing instruments equipped a mechanism in which a sign of exhausting an ink can be detected have not so far been available.
Accordingly, in the writing instruments having the above structures, it is not before an ink is used until starving is caused during writing that the ink is found to be exhausted, and then the writing instrument is disposed or reused with supplementing the ink. However, starving is caused as well due to drying of the pen tip, and therefore if starving is caused due to drying of the pen tip though the ink impregnated into the ink occlusion body sufficiently remains, it is not a substantial sign of exhausting the ink, and a problem on use is involved therein.
On the other hand, disclosed in Japanese Patent Application Laid-Open No. 270585/1994 is a writing instrument in which a sliver working as an ink occlusion body is mounted in a transparent barrel to feed a pen tip in a writing part with an ink impregnated in the above sliver and in which the inside of the writing instrument can be visually observed from the sliver up to the pen tip.
However, in a writing instrument having the above structure, when an amount of an ink occluded in a sliver is decreased, an remaining amount of the ink can be observed to some extent by the degree in the color of the ink occluded in the sliver, but a sign of exhausting the ink can not surely be detected. Accordingly, a problem on use is involved as well in the above writing instrument.
In light of the problems of the conventional techniques and the existing situation each described above, the present invention intends to solve them, and an object of the present invention is to provide a writing instrument in which a pen tip in a writing part is fed with an ink for a writing instrument such as a water-based ink or an oil-based ink impregnated into an ink occlusion body in a barrel, wherein a sign of exhausting the ink can readily and surely be detected, and another object thereof is to provide a writing instrument in which a consumption rate of the ink impregnated into an ink occlusion body is further improved.